Co-evolution of a planetesimal eccentricity and orbital precession when acted upon by an eccentric perturber. Since the planetesimal orbit precesses, its periastron will eventually be aligned with that of the perturber on the same side of the massive central body, that is, the longitudes of periastra of the planetesimal and the perturber are equal (ϖ = 0). In this configuration, the planetesimal eccentricity is maximum.